Until recently batteries and battery packs for portable devices have been viewed somewhat as low technology level components of more sophisticated systems. Certainly this is true when the battery pack is compared to a host device such as portable, or "laptop" computers, cellular phones, and two way hand held radios. Virtually all such devices employ microcontrollers and sophisticated software to control various functions and perform various tasks, while battery packs for these devices have traditionally been low technology components. This has resulted in the host device being by far the most valuable component of a system. Accordingly, devices such as, for example, laptop computers, have been the target of theft at an increasing rate.
To deter theft of these devices, certain measures have been taken. For example, cellular phones have unique identifiers which prevent unauthorized individuals from establishing fraudulent communications links, and software is used by many devices to "lock out" unauthorized users with password protection. For the most part, battery packs have not been seen as a lucrative item for such pilferage, and no theft deterrent measures have been employed in battery packs. However, with the advent of "smart" battery packs, this will likely change.
Smart battery packs are battery packs that contain sophisticated circuitry, such as a microprocessor or equivalent. The utility of such battery packs has been proven in the marketplace, and they perform a variety of functions such capacity or "fuel" gauging, charge control, and safety to name but a few. It has been found that the higher cost of these high technology battery packs is outweighed by the increase in efficiency yielded by the electronics. This has made smart battery packs desirable in many markets, particularly portable computers. Since smart battery packs are significantly more valuable than their low technology predecessors, it is likely that theft of such battery packs will increase as well. Therefore, there exists a need in a smart battery pack for a theft deterrent circuit, and particularly one which disables the battery pack from unauthorized use.